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stepladder [879]
3 years ago
9

Which of the following indicates that an exothermic reaction has taken place?

Chemistry
2 answers:
Tomtit [17]3 years ago
4 0
<h2>Answer:</h2>

The option B is correct option. Which is release of heat and/or light energy .

<h3>Explanation:</h3>

According to the definition of exothermic reaction :

<em>An exothermic reaction is a chemical reaction that releases energy by light or heat.</em>

From definition option B (release of heat and/or light energy) indicates that an exothermic reaction has taken place.



.

mote1985 [20]3 years ago
4 0

Answer: Option (B) is the correct answer.

Explanation:

An exothermic reaction is defined as the chemical reaction in which there occurs release of heat.

For example, A + B \rightarrow AB + Heat

In an exothermic reaction, energy of reactants is more than the energy of products.

Whereas an endothermic reaction is defined as a chemical reaction in which heat is absorbed by reactant molecules.

For example, A + B + Heat \rightarrow AB

In endothermic reaction, energy of reactant molecules is less than the energy of products.

Thus, we can conclude that release of heat and/or light energy indicates that an exothermic reaction has taken place.

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You place 36.5 ml of 0.266 M Ba(OH)2 in a coffee-cup calorimeter at 25.00°C and add 56.6 ml of 0.648 M HCl, also at 25.00°C. Aft
olya-2409 [2.1K]

Answer : The enthalpy of reaction (\Delta H_{rxn}) is, -96.9 kJ/mole

Explanation :

First we have to calculate the mass of solution.

Mass=Density\times Volume

Volume of solution = Volume of HCl + Volume of Ba(OH)_2

Volume of solution = 56.6 mL + 36.5 mL

Volume of solution = 93.1 mL

Density of solution = 1 g/mL

Mass=1g/mL\times 93.1mL=93.1g

The mass of solution is, 93.1 grams.

Now we have to calculate the heat released in the system.

Formula used :

Q=m\times c\times \Delta T

or,

Q=m\times c\times (T_2-T_1)

where,

Q = heat released = ?

m = mass = 93.1 g

C_p = specific heat capacity of water = 4.184J/g^oC

T_1 = initial temperature  = 25.0^oC

T_2 = final temperature  = 29.83^oC

Now put all the given value in the above formula, we get:

Q=93.1g\times 4.184J/g^oC\times (29.83-25.00)^ioC

Q=1881.43J=1.88kJ        (1 kJ = 1000 J)

Now we have to calculate the moles of Ba(OH)_2 and HCl.

\text{Moles of }Ba(OH)_2=\text{Concentration of }Ba(OH)_2\times \text{Volume of solution}

\text{Moles of }Ba(OH)_2=0.266M\times 0.0365L=9.71\times 10^{-3}mol

and,

\text{Moles of }HCl=\text{Concentration of }HCl\times \text{Volume of solution}

\text{Moles of }HCl=0.648M\times 0.0566L=3.66\times 10^{-2}mol

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

Ba(OH)_2+2HCl\rightarrow BaCl_2+2H_2O

From the balanced reaction we conclude that

As, 1 mole of Ba(OH)_2 react with 2 mole of HCl

So, 9.71\times 10^{-3}  moles of Ba(OH)_2 react with 9.71\times 10^{-3}\times 2=0.0194 moles of HCl

From this we conclude that, HCl is an excess reagent because the given moles are greater than the required moles and Ba(OH)_2 is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of H_2O

From the reaction, we conclude that

As, 1 mole of Ba(OH)_2 react to give 2 mole of H_2O

So, 9.71\times 10^{-3}  moles of Ba(OH)_2 react with 9.71\times 10^{-3}\times 2=0.0194 moles of H_2O

Now we have to calculate the change in enthalpy of the reaction.

\Delta H_{rxn}=-\frac{q}{n}

where,

\Delta H_{rxn} = enthalpy of reaction = ?

q = heat of reaction = 1.88 kJ

n = moles of reaction = 0.0194 mole

Now put all the given values in above expression, we get:

\Delta H_{rxn}=-\frac{1.88kJ}{0.0194mole}=-96.9kJ/mole

The negative sign indicates that the heat is released.

Therefore, the enthalpy of reaction (\Delta H_{rxn}) is, -96.9 kJ/mole

3 0
3 years ago
How many molecules are in 7V205?​
elixir [45]

Answer:

Calculate the number of moles you have by taking the Mass / molar mass. if you have 1000 grams ; then 1,000 g / 151.001 g/mol = X g moles. Then multiply by Avogadros # = 6.022140857 × 10^23 molecules per g mole. The result is the # of molecules of MnSO4

Explanation: Hope this helps

7 0
3 years ago
The following equation shows the correct molecules formed in the reaction, but the products are incorrect. CH4 +202=H20+ CO2 How
Hunter-Best [27]
For the equation to balance out, you would need 2 H2O on the product. That will give a total of 1 Carbon, 4 Hydrogens and 4 Oxygens on each side.
5 0
3 years ago
Which pair of elements can be used to determine the age of a fossil that is over one billion years old?
lakkis [162]

Answer:

Explanation:

There are some radioactive nuclides can be used to measure time on an archeological scale. One is the best example of this is radiocarbon dating. This process is based on the ratio of caebon-14 to carbon-12 in the atmosphere which is relatively constant.

The half time of C-14 5730 years  

Carbon-14 is a radioactive nucleus. It has a half-life of 5730 years.

All living tissues like plants and animal absorbed carbon-12 along with carbon-14 with same ratio of caebon-14 to carbon-12 in the atmosphere.

Carbon-14 dating is based on the ratio of carbon-14 to carbon-12 in the atmosphere which is relatively constant

3 0
3 years ago
Read 3 more answers
hi, can you check if my answers are correct? I'm not so confident in this topic (topic: Classifying Types of Chemical Reactions)
NikAS [45]
I am pretty sure your answer are correct , from what I know. Good job!
7 0
3 years ago
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